f2fs: introduce a shrinker for mounted fs
This patch introduces a shrinker targeting to reduce memory footprint consumed
by a number of in-memory f2fs data structures.
In addition, it newly adds:
- sbi->umount_mutex to avoid data races on shrinker and put_super
- sbi->shruinker_run_no to not revisit objects
Note that the basic implementation was copied from fs/ubifs/shrinker.c
Reviewed-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/shrinker.c b/fs/f2fs/shrinker.c
new file mode 100644
index 0000000..16e9b43
--- /dev/null
+++ b/fs/f2fs/shrinker.c
@@ -0,0 +1,104 @@
+/*
+ * f2fs shrinker support
+ * the basic infra was copied from fs/ubifs/shrinker.c
+ *
+ * Copyright (c) 2015 Motorola Mobility
+ * Copyright (c) 2015 Jaegeuk Kim <jaegeuk@kernel.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+#include <linux/fs.h>
+#include <linux/f2fs_fs.h>
+
+#include "f2fs.h"
+
+static LIST_HEAD(f2fs_list);
+static DEFINE_SPINLOCK(f2fs_list_lock);
+static unsigned int shrinker_run_no;
+
+unsigned long f2fs_shrink_count(struct shrinker *shrink,
+ struct shrink_control *sc)
+{
+ struct f2fs_sb_info *sbi;
+ struct list_head *p;
+ unsigned long count = 0;
+
+ spin_lock(&f2fs_list_lock);
+ p = f2fs_list.next;
+ while (p != &f2fs_list) {
+ sbi = list_entry(p, struct f2fs_sb_info, s_list);
+
+ /* stop f2fs_put_super */
+ if (!mutex_trylock(&sbi->umount_mutex)) {
+ p = p->next;
+ continue;
+ }
+ spin_unlock(&f2fs_list_lock);
+
+ /* TODO: count # of objects */
+
+ spin_lock(&f2fs_list_lock);
+ p = p->next;
+ mutex_unlock(&sbi->umount_mutex);
+ }
+ spin_unlock(&f2fs_list_lock);
+ return count;
+}
+
+unsigned long f2fs_shrink_scan(struct shrinker *shrink,
+ struct shrink_control *sc)
+{
+ unsigned long nr = sc->nr_to_scan;
+ struct f2fs_sb_info *sbi;
+ struct list_head *p;
+ unsigned int run_no;
+ unsigned long freed = 0;
+
+ spin_lock(&f2fs_list_lock);
+ do {
+ run_no = ++shrinker_run_no;
+ } while (run_no == 0);
+ p = f2fs_list.next;
+ while (p != &f2fs_list) {
+ sbi = list_entry(p, struct f2fs_sb_info, s_list);
+
+ if (sbi->shrinker_run_no == run_no)
+ break;
+
+ /* stop f2fs_put_super */
+ if (!mutex_trylock(&sbi->umount_mutex)) {
+ p = p->next;
+ continue;
+ }
+ spin_unlock(&f2fs_list_lock);
+
+ sbi->shrinker_run_no = run_no;
+
+ /* TODO: shrink caches */
+
+ spin_lock(&f2fs_list_lock);
+ p = p->next;
+ list_move_tail(&sbi->s_list, &f2fs_list);
+ mutex_unlock(&sbi->umount_mutex);
+ if (freed >= nr)
+ break;
+ }
+ spin_unlock(&f2fs_list_lock);
+ return freed;
+}
+
+void f2fs_join_shrinker(struct f2fs_sb_info *sbi)
+{
+ spin_lock(&f2fs_list_lock);
+ list_add_tail(&sbi->s_list, &f2fs_list);
+ spin_unlock(&f2fs_list_lock);
+}
+
+void f2fs_leave_shrinker(struct f2fs_sb_info *sbi)
+{
+ spin_lock(&f2fs_list_lock);
+ list_del(&sbi->s_list);
+ spin_unlock(&f2fs_list_lock);
+}